The invention relates to a process for producing large wall elements which contain at least two layersxe2x80x94an outer layer and a loadbearing or intermediate layerxe2x80x94and internal fittings and are intended to be used as constructional elements for buildings, in particular low-energy houses, and moreover to an apparatus for carrying out the process and also to a shuttering element for use in the process and to large wall elements produced in accordance with the process, in particular thermally insulating wall elements.
Processes and apparatus for producing wall elements for buildings are known. An appropriate apparatus is described, for example, in WO 96/24476. This is a table which is fixed in the horizontal and on which the wall elements are produced. As a rule, shuttering or a casting trough, in which a wall element can be produced, is arranged on said table. On the surface of these tables, there is generally only space for one wall element in each case because of their large format; the relevant wall elements can have a length of up to 20 meters and more. If, however as is done according to the prior art, not only the shuttering elements are intrinsically produced in the horizontal but also their concrete core or the concrete part of the wall element, then efficient production of the wall elements is only possible when a plurality of production tables are used for the production, in order in particular to decouple the operation of constructing a shuttering element and the setting of the concrete. Because of the large dimensions of the wall elements, already mentioned, the mass production of standardized wall elements primarily entails the provision of very large production halls, as a result of which the production costs are increased to a not inconsiderable extent. In addition, the problem occurs that within the context of the production process, the wall elements are often damaged when being removed from the shuttering, which means that comprehensive reworking is necessary, which likewise increases the production costs. Furthermore, in the case of the known apparatus, it proves to be difficult to load the wall element produced onto a suitable transporter without damage. This difficulty is based, inter alia, on the fact that after the addition of concrete, the finished wall elements have a weight which is so high that only a very complicated lifting mechanism is capable of heaving the wall elements out of the horizontal without damage.
The invention is therefore based on the object of providing a process and an apparatus which reduces the outlay on production and costs for wall elements considerably.
This object is achieved in an extremely surprising way by the features of claim 1. Advantageous and preferred developments form the subject of the subclaims.
In detail, a tilting table formed as a large angle is provided, whose one leg inner side is used to construct a stack of wall elements. The stack leans on the inside of the other leg and is closed and pressed together by a cover. By rotating the tilting table through 90xc2x0, the previously horizontal wall elements are set vertical and the interspaces are filled with concrete, which, following the setting of the concrete, results in a multiplicity of large wall elements standing one beside another, which can be used for the outer and inner walls and for floors of buildings.
It should be pointed out that reference is made to the disclosure of German patent application 197 33 755.4-25 in its entirety.
In an advantageous way, in a development of the invention, the tilting table is rotatably fixed on a holding apparatus. In particular in order to carry out the tilting movement with reference to the supporting surface, it has proven to be very advantageous in the apparatus according to the invention if the rotatable suspension or mounting is provided substantially at the center of gravity of the tilting table. Undesired torques, which lead to destabilizing the tilting table and therefore have to be compensated for, can be avoided in this way. In addition, such a center-of-gravity mounting makes it possible for the tilting apparatus to be moved into various tilted positions without great expenditure of force. To this extent, it requires only a comparatively low-power pivoting device, so that, in spite of the high loads, rotation by hand is also possible. Manual operation can in particular be provided for the case in which a defect occurs in a motor-controlled pivoting device.
As already outlined in the patent application 197 33 755.4-25, a plurality of wall elements are produced in a stack one above another on the construction surface, so that each previously produced wall element is used as a working surface for the production of a successive wall element. Accordingly, during the construction of the wall elements, the working height for the persons working on the wall elements changes in each case. In order to correct this change in height during the production process, a lifting apparatus has been disposed on the tilting table, by means of which it is possible to lift and lower but also hold at a definable height. Furthermore, in the tilting table according to the invention, the rotated wall element can be let down into a pit, which is still to be described below, and the filling of the wall element with concrete can be filled directly from the outlet opening of concrete mixing vehicles, without any pumps having to be used in the process. The lifting apparatus advantageously also grips at the center of gravity of the tilting table, which also avoids the occurrence of lateral forces here.
In a development of the invention, the apparatus according to the invention additionally has the aforementioned pit area for the introduction of the bearing apparatus. The pit area is substantially used for lowering the tilting table in the course of the production of the wall-element stack. The possibility of lowering makes it readily possible to adapt the tilting table to the working height, without scaffolding constructions, which are problematic in terms of safety, having to be used for this adaptation. Furthermore, it has proven to be advantageous if parts of the operation of pivoting the tilting table are carried out inside the pit. As a result, the risks which occur during the tilting of the loaded supporting surfaces, for example for the persons involved in the wall element production, can be significantly reduced. In addition, as is obvious to those skilled in the art, this means that there is a further saving in space in the production of the wall elements, since relatively large areas having to be blocked off during the tilting operation are no longer needed.
In order not to have to configure the pit area to be too large, it has proven to be advantageous in practice if, following the production of a wall element stack, the actions of rotating and lifting the stack out of the pit are carried out in a synchronized rotating and lifting movement. In this case, depending on the depth of the pit area, the pit width can be restricted to virtually an area diagonal of a lateral end face of the tilting table.
Furthermore, it has been shown in practice that, in particular during the drying of the concrete of the wall elements, it is necessary to have a high degree of planarity of the surface on which the wall elements are supported during the drying, in order to prevent any possible distortion of the wall elements. The apparatus according to the invention therefore also comprises a specific support, directed to the size of the wall elements produced, which is preferably fitted at the bottom of the pit area. In particular, double-T girders which reach over the entire length of the wall elements and which, in the apparatus according to the invention, have a deviation in the vertical direction substantially below 9 mm have been tried and tested for this support. In order to obtain substantially optimal mounting of the loaded tilting table, it has proven to be advantageous to dispose at least three double T girders in parallel underneath the construction surface or supporting surfaces. In order to load the girders uniformly, one is disposed at the angle of the tilting table, the other centrally and the third at the end of the construction surface.
For the tilting table according to the invention, supporting surfaces of preferably up to 22 m can be used, so that a high degree of flexibility in the production of long wall elements is also provided. It is therefore also possible, for example, to use the wall elements produced over the entire lengths of the supporting surface in such a way that the long side of the finished wall element represents the entire height of the building to be erected.
The flexibility of the apparatus according to the invention is also increased by the fact that the supporting surfaces forming the tilting table can be used as a construction surface or wall-element supporting surface, as expedient. This can be advantageous in particular if the architecture of a predefined working area prescribes one access direction to the tilting table. In this case, the tilting table substantially comprises three girder profiles which are connected to one another. The basic element used for the tilting table is substantially a girder profile welded rigidly to form a right angle, to whose free legs reinforced profiles can be fastened in order to lengthen them. The lengthened legs are then used as a supporting surface for the wall elements to be produced. The tilting table, in the dismantled or non-assembled state, can accordingly be loaded and transported in a simple way in a conventional open-top container. In addition, the girder profiles used provide sufficient stability to bear even the heaviest loads.
A necessary and expedient further refinement of the present invention is also to be seen in the fact that a covering apparatus is provided which can be fastened to the tilting table and which permits a press connection between the tilting table and one or more wall elements applied in a stack to the construction surface. By means of this press connection, firstly the wall elements can be secured to the tilting table, so that during the pivoting of the tilting table, the wall elements are held or pressed laterally on the supporting surfaces and, secondly, the press connection is used for the lateral support of the shuttering of the wall elements as the concrete is put into the wall elements that have been turned into the vertical. In order to compensate for the pressure which is produced on the shuttering by putting the concrete into the shuttering of the wall elements, it has been shown in practice that substantially optimal planarity of the wall elements can be ensured if the covering apparatus is equipped for a pressing pressure of about 1.5 t/m2.
The tilting table permits the walls of a single-occupancy dwelling to be produced in one or two batches. This considerable mass of concrete makes it possible to dispense with the otherwise conventional steam hardening of concrete during the production of individual wall elements, since the heat which is released during setting is adequate to reach the desired elevated temperature of the setting concrete mass. In order to avoid the temperature drop of the wall elements standing at the edge, the wall elements for the outer walls of the building are arranged with their thick thermally insulating layer on the underside or upper side of the stack and, in this way, the loss of heat to the side is avoided (during the casting of the walls, the stack is rotated through 90xc2x0).
In the novel production process for the large wall elements, use is additionally made of the circumstance that said large wall elements are desired with thermally insulating outer layers or in a sandwich design. These thermally insulating layers are used as shuttering for the concrete core of the large wall elements, to be specific, this is achieved by suitable spacers of concrete webs being available, and keeping these layers at the correct distance from one another as shuttering walls. The compressive strengths of thermally insulating layers is not very high, for which reason the spacers should have a large contact area on their bearing side toward the thermally insulating layers. This is achieved by means of handle-like spacers, such as have been described by EP 0 299 353. These spacers, with their flange-like ends, are pressed into the thermally insulating layers slightly during the compression of the stack and are therefore held by clamping after the stack has been rotated through 90xc2x0 and the wide end faces of the spacers run vertically. There is therefore no need to have recourse to the retaining force of the binder which has been introduced between the end face of the spacer and the adjacent thermally insulating layer during the construction of the stack and which is used for the purpose of ensuring good adhesion between the thermally insulating layer and the concrete layer. This means that, during the production of the large wall elements, there is a free choice as to whether wall elements with two or three layers are constructed.
One critical point in buildings is the mutual connection of the large wall elements constituting the walls or floors. Large wall elements which meet one another at the corners are given a miter bevel and, in addition, a coupling space, which in each case comprises a depression extending longitudinally in the miter bevel and into which coupling space reinforcing loops project and, in this coupling space, form an eye through which a coupling rod of structural steel can be pushed in order to connect the adjacent walls or floors to one another. During the production of the building, the coupling space is filled with cast concrete, so that the reinforcement in the one large wall element is continued, via the coupling space, into the reinforcement of the other large wall element. The invention also deals with the production of these coupling spaces and the reinforcement loops reaching into them.
In addition to connecting wall elements via miter bevels, there is also the connection via a butt joint, that is to say the narrow side of a wall element adjoins the wide side of another wall element and has to be connected permanently to the latter. For this purpose, filling a coupling cavity with cast concrete is likewise provided, in which cavity reinforcing loops are coupled to one another by a transverse rod. In order not to disturb the production of the wall elements, the reinforcing loops on the wide side of the wall element are turned over into the plane of the wall element, that is to say use is made of reinforcing brackets with bent-over loops or eyes during the production of the wall elements, and these bent-over portions are bent up again when the building is being erected, so that the loops or eyes project from the plane of the wide sides of the wall elements and can be coupled to the reinforcing loops on the narrow side of the adjacent wall elements by pressing a rod transversely through.